Re: [PATCH] drm/rockchip: cancel pending vblanks on close

From: Mark yao
Date: Sun Mar 13 2016 - 22:40:23 EST

On 2016å03æ12æ 01:21, John Keeping wrote:
When closing the DRM device while a vblank is pending, we access
file_priv after it has been free'd, which gives:

Unable to handle kernel NULL pointer dereference at virtual address 00000000
PC is at __list_add+0x5c/0xe8
LR is at send_vblank_event+0x54/0x1f0
[<c02952e8>] (__list_add) from [<c031a7b4>] (send_vblank_event+0x54/0x1f0)
[<c031a760>] (send_vblank_event) from [<c031a9c0>] (drm_send_vblank_event+0x70/0x78)
[<c031a950>] (drm_send_vblank_event) from [<c031a9f8>] (drm_crtc_send_vblank_event+0x30/0x34)
[<c031a9c8>] (drm_crtc_send_vblank_event) from [<c0339ad8>] (vop_isr+0x224/0x28c)
[<c03398b4>] (vop_isr) from [<c0081780>] (handle_irq_event_percpu+0x12c/0x3e4)

This can be triggered somewhat reliably with:

modetest -M rockchip -v -s ...

Add a preclose hook to the driver so that we can discard any pending
vblank events when the device is closed.

Signed-off-by: John Keeping <john@xxxxxxxxxxxx>

Looks good for me, applied into my drm-fixes.

Thanks for the fix.

ïark Yao